Most people develop a dominant hand early in childhood as the brain streamlines motor control for everyday tasks. Handedness reflects how motor planning and fine control are distributed across networks in both hemispheres, not a simple “left brain vs. right brain” split. Using the non-dominant hand typically feels slower and less precise because those motor programs are less practiced and require more attention to execute.
Neuroplasticity is the brain’s capacity to change its structure and function in response to experience. Practice that is novel, effortful, and repeated tends to drive the biggest, most specific changes - often localized to the circuits engaged by the skill being learned. In this context, non-dominant-hand writing is a form of fine-motor training: improvements are expected to be skill- and context-specific rather than global boosts to cognition. People sometimes explore it for curiosity, rehabilitation, or to add deliberate challenge to routine tasks.